American twins,Brit triple spool engines?
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
411A, would you please substantiate your notation in the following paragraph with good data to prove your point, and not just loose talk off the top of your noggin:-
Thank you Sir.
"Rollers consume more fuel than their GE counterparts. Nope, not the case, when you compare the L1011 with the DC10, at equal in-flight weights".
(I'm even sceptical about some data that I look at nowadays!!)
Darn it anyway, this copy and paste previous quotes just does not work for me and it is frustrating......sorry folk.
Thank you Sir.
"Rollers consume more fuel than their GE counterparts. Nope, not the case, when you compare the L1011 with the DC10, at equal in-flight weights".
(I'm even sceptical about some data that I look at nowadays!!)
Darn it anyway, this copy and paste previous quotes just does not work for me and it is frustrating......sorry folk.
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
Just take a listen to this old clanker winding up.
I keep thinking of this old timer engine taking it's time to flash up. Man, this grinding and fan blade clanking and belching of smoke is something else to hear and see. One could almost have gone for a good hearty breakfast and been back in time
Not much wonder Stewart and his greenies around LHR banded together to almost shut the works down at this airport, having to see this smoke and noise. Even the current models of Trents are slow dogs during start-up and like to belch out some smoke.
411A, you probably had your hands on the horns of this old frame for some trips. Some of your nervous pax must have just about freaked out listening to this start performance!
Just be patient and listen to all of this video. You'll shake your head at this pathetic performance.
YouTube - L-1011 N700TS Airline History Museum 1
Not much wonder Stewart and his greenies around LHR banded together to almost shut the works down at this airport, having to see this smoke and noise. Even the current models of Trents are slow dogs during start-up and like to belch out some smoke.
411A, you probably had your hands on the horns of this old frame for some trips. Some of your nervous pax must have just about freaked out listening to this start performance!
Just be patient and listen to all of this video. You'll shake your head at this pathetic performance.
YouTube - L-1011 N700TS Airline History Museum 1
Guest
Posts: n/a
411A
The only thing I can fathom from your comments is that you are setting up the Lockheed to garner compliments for its slippery airframe, one that makes a gas pig look lean.
If that is the case, I would agree. Lockheed likes clean, MD likes stout. Airforce Navy thing.
bear
The only thing I can fathom from your comments is that you are setting up the Lockheed to garner compliments for its slippery airframe, one that makes a gas pig look lean.
If that is the case, I would agree. Lockheed likes clean, MD likes stout. Airforce Navy thing.
bear
Usual disclaimers apply!
Join Date: Nov 1999
Location: EGGW
Posts: 843
Likes: 0
Received 0 Likes
on
0 Posts
Er no! Actually a hung start. The L1011 apu could be marginal on air delivery at times and that would slow up the start cycle. Looking at the amount of smoke I'd say the engine fuel system was full of inhibiting oil.
If starter air wasn't the issue, from memory I'd pull the plug from the SFFR until the engine was up and running, that would speed up the acceleration.
If starter air wasn't the issue, from memory I'd pull the plug from the SFFR until the engine was up and running, that would speed up the acceleration.
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
Weight comparisons.
GE: CF6-80E1
Dry Weight: 5091.62 kg (11225 lb).
Includes all basic engine accessories and optional equipment as listed in the manufacturer’s engine specs.
http://easa.europa.eu/certification/...1-14062004.pdf
RR: T700 series.
Dry Weight: 6160 kg (13580 lb).
(Not including fluids and Nacelle EBU)
http://easa.europa.eu/certification/...1-06032006.pdf
Dry Weight: 5091.62 kg (11225 lb).
Includes all basic engine accessories and optional equipment as listed in the manufacturer’s engine specs.
http://easa.europa.eu/certification/...1-14062004.pdf
RR: T700 series.
Dry Weight: 6160 kg (13580 lb).
(Not including fluids and Nacelle EBU)
http://easa.europa.eu/certification/...1-06032006.pdf
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
411A, would you please substantiate your notation in the following paragraph with good data to prove your point, and not just loose talk off the top of your noggin:-
Thank you Sir.
Thank you Sir.
Operating statistics, 1999
DC10-30 fuel consumption 2,693 USG/hr, operating cost $5,972/hr
L1011-200 fuel consumption 2,447 USG/hr, operating cost $4,891/hr.
You're welcome.
NB. Of course, the DC10 might have been dragging a boat anchor...
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
Sorry, no link available from my end, this was info provided at an ATA conference I attended some years ago.
I'm sure you can find a link (although the data ia slightly outdated now, due to not many of these aircraft in service any longer).
I suspect the larger fuel consumption of the DC10 is due in part to the specific location of the number two engine.
I'm sure you can find a link (although the data ia slightly outdated now, due to not many of these aircraft in service any longer).
I suspect the larger fuel consumption of the DC10 is due in part to the specific location of the number two engine.
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
This is not a good comparison 411A, as the 10-30 was packing 53 tons more than the L1011. As well, different planform, airfoils and even more differences between the two.
MTOW of the DC10-30 is 572,000lbs.
MTOW of the L1011-200 is 466,000 lbs.
http://www.caa.co.uk/docs/702/3GE069_01102004.pdf
CF6-50A rated at 218.3 kn.
T/off - 2.168 kg/s
C/out - 1.787 kg/s
Idle - 0.163
http://www.caa.co.uk/docs/702/1RR005_01102004.pdf
RB211-524B rated at 218.5 kn.
Take-off - 2.21 kg/s.
Climb-out - 1.79 kg/s.
Idle - 0.24.
So the '10-30 with a CF6-50A engine was burning less fuel in the above noted three flight phases than the the RB211-524B in the L-1011-200.
Mach .04 in favor of the L1011 for cruise speed but 53 tons lighter than the 10.
MTOW of the DC10-30 is 572,000lbs.
MTOW of the L1011-200 is 466,000 lbs.
http://www.caa.co.uk/docs/702/3GE069_01102004.pdf
CF6-50A rated at 218.3 kn.
T/off - 2.168 kg/s
C/out - 1.787 kg/s
Idle - 0.163
http://www.caa.co.uk/docs/702/1RR005_01102004.pdf
RB211-524B rated at 218.5 kn.
Take-off - 2.21 kg/s.
Climb-out - 1.79 kg/s.
Idle - 0.24.
So the '10-30 with a CF6-50A engine was burning less fuel in the above noted three flight phases than the the RB211-524B in the L-1011-200.
Mach .04 in favor of the L1011 for cruise speed but 53 tons lighter than the 10.
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
The 'S' duct for the #2 eng in the L1011 would be 'chocking' off some airflow to the engine in the L1011 resulting in less efficient thrust, a disadvantage when compared to the straight thru airflow in the '10.
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
Another reason for the RRs being a tad heavier in the CF6 and RB211-524 engines is in the wall thickness of the casings from the LPC all the way back to the HPT. This helps in longtidunal rigidity of the engine. Yet, RR copied GE by using the thrust link arrangement, (aluminum pipe) that ties the aft eng mount to the fwd eng mount to increase stability even some more.......go figure?
Rapid throttle movements aggravates longitudinal bowing of the casing and should be avoided.
Also for the Rolls, the IPC drum and it's associated compressor blades and stator blades including the drive shaft and associated bearings/housing and spoked support struts weigh more than an extra N2 compressor disk/blades and VSV linkages as in the twin spool GE/Pratt designs.
When twin spools can do the job more efficiently why 'over engineer' the engine by adding more spools and it's associated hardware as RR do, making it more complex and costly from a manufacturing and maintenance aspect, yet achieving a similar thrust output.
Rapid throttle movements aggravates longitudinal bowing of the casing and should be avoided.
Also for the Rolls, the IPC drum and it's associated compressor blades and stator blades including the drive shaft and associated bearings/housing and spoked support struts weigh more than an extra N2 compressor disk/blades and VSV linkages as in the twin spool GE/Pratt designs.
When twin spools can do the job more efficiently why 'over engineer' the engine by adding more spools and it's associated hardware as RR do, making it more complex and costly from a manufacturing and maintenance aspect, yet achieving a similar thrust output.
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
The 'S' duct for the #2 eng in the L1011 would be 'chocking' off some airflow to the engine in the L1011 resulting in less efficient thrust, a disadvantage when compared to the straight thru airflow in the '10.
...as the 10-30 was packing 53 tons more than the L1011
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
The DC-10/MD-11 #2 engine does create a substantial nose-down moment which must be reacted by the horizontal tail. In this respect it's at some disadvantage compared to the L-1011.
And MD-11 crew have said that a sudden #2 failure in cruise creates a wild ride until they can re-trim.
And MD-11 crew have said that a sudden #2 failure in cruise creates a wild ride until they can re-trim.
There are one or two blinkered views being expressed here.
I have no axe to grind, however one thing that hasn't been mentioned is the line maintenance friendlyness of the different engines. For my part the RB211/Trent has always been easier due to the ancilllary equipment being hung on the outside of the fan case. The GE and PW engines have the equipment hung against the core. It's a hell of a lot quicker on a tight turn round to lift a fan cowl than it is to pump open the T/Rev halves. Admittedly, the PDOS helps with the bigger GE engines but it still has caused delays.
I also remember the first time I saw a CF6 with the cowls off, compared to the '211 it looked incredibly complex with all those VSVs and control linkages. Works very well though and lasts a long time.
Regarding the DC10/Tristar spat. The No.2 engine on both was right royal pain in the backside. But at least the '10 had a platform to work from, in the Tristar one would be sliding around in a pool of oil all night.
Happy days.
I have no axe to grind, however one thing that hasn't been mentioned is the line maintenance friendlyness of the different engines. For my part the RB211/Trent has always been easier due to the ancilllary equipment being hung on the outside of the fan case. The GE and PW engines have the equipment hung against the core. It's a hell of a lot quicker on a tight turn round to lift a fan cowl than it is to pump open the T/Rev halves. Admittedly, the PDOS helps with the bigger GE engines but it still has caused delays.
I also remember the first time I saw a CF6 with the cowls off, compared to the '211 it looked incredibly complex with all those VSVs and control linkages. Works very well though and lasts a long time.
Regarding the DC10/Tristar spat. The No.2 engine on both was right royal pain in the backside. But at least the '10 had a platform to work from, in the Tristar one would be sliding around in a pool of oil all night.
Happy days.
Join Date: Dec 2010
Location: Europe
Age: 88
Posts: 290
Likes: 0
Received 0 Likes
on
0 Posts
Note: The GE engined aircraft has the best range as indicated on the Airbus graphs.
UT has made a good case for saying that the GE engine has a better fuel consumption than the RR design, but the question was not does GE do better than RR, but what are the advantages of two shaft engines against three shaft designs.
The debate about relative fuel burn at take-off, climb and approach doesn't really address the question since by far the biggest amount of fuel is consumed in cruise and so far as I am aware there is no simple relationship between TO and cruise sfc performance, it depending amongst other things on the BPR (and cruise thrust matters as well). The only truly valid comparison I have seen mentioned in this debate is that given by UT as quoted above. These are estimates by a single manufacturer, for the same airframe and for the same MZFW and TOW, i.e. the same amount of fuel on board and as such should give a coherent assessment of relative performance on real missions.
Sure, the GE aircraft with new engines goes farther, but it isn't all that much of a difference. The graphs are not all that big, but my reading for range taken from the AI graphs is, with 175t MZFW and 233t TOW:
@ Max structural P/L/MTOW PW4000 - 3700 n.mls, RR - 3700 n.mls, GE 90 - 3750 n.mls
@MTOW/Max tankage PW4000 - 5500 n.mls, RR - 5500 n.mls, GE90 - 5550 n.mls
@ Max tankage/zero P/L PW4000 - 6500 n.mls, RR - 6500 n.mls, GE90 - 6600 n.mls
In other words the GE is about 1% better than either the PW4000 or the RR engines when new, but that is a difference that could be easily lost by deterioration.
Some airlines ask for, and are given, performance guarantees to be met after X years in service, so the retention of performance is also very important. Without, as put earlier, wanting to get into a pissing contest, I have to say that when I was in work the RR engines had a good reputation in this respect - certainly there was less heart searching about giving 'in service' guarantees if the airline had chosen RR engines.
What might one deduce from this?
I would say since the PW engines are 2 shaft and identical to the 3 shaft design in aircraft performance terms one cannot conclude superiority of 2 shafts over 3 so far as fuel consumption is concerned, just that one company has better technology than the other two.
Other issues of cost, maintainability and reliability I leave to others who are better informed
Join Date: Dec 2003
Location: On the ground for now.
Posts: 274
Likes: 0
Received 0 Likes
on
0 Posts
Clive and Turin.
Thanks for your contribution which makes this thread interesting and I will admit, I am always learning throughout my lifetime.
Let's try and stay on topic asit's so easy for thread creep by going off on a tangent like Tristar vs DC10 stuff.
Thanks for your contribution which makes this thread interesting and I will admit, I am always learning throughout my lifetime.
Let's try and stay on topic asit's so easy for thread creep by going off on a tangent like Tristar vs DC10 stuff.